Argentohalide complex film construction

ABSTRACT

THIS INVENTION DISCLOSES A FILM HAVING AT LEAST ONE LAYER CONTAINING A LIGHT INSENSITIVE ARGENTOHALIDE COMPLEX, SAID LAYER BEING FREE OF PROTIC SOLVENT, PHOTOSENSITIVE SILVER HALIDE CRYSTALS AND PHOTOSENSITIVE SILVER IONS, SAID COMPLEX PROVIDING LIGHT SENSITIVE SILVER HALIDE IN SAID LAYER UPON CONTACT WITH A PROTIC SOLVENT. SUCH FILMS CAN BE UTILIZED BY CONTACTING THE LAYER CONTAINING THE LIGHT INSENSITIVE ARGENTOHALIDE COMPLEX WITH A PROTIC SOLVENT, RESULTING IN THE GENERATION OF PHOTOSENSITIVE SILVER HALIDE, AND EXPOSING AND DEVELOPING PHOTOSENSITIVE SILVER HALIDE BY CONVENTIONAL PHOTOGRAPHIC TECHNOLOGY.

United States Patent 3,600,175 ARGENTOHALIDE COMPLEX FILM CONSTRUCTIONGeorge de W. Anderson, near Bishops, Stortford, and

Grahame J. Stehle, Ilford, England, assignors to Minggsota Mining andManufacturing Company, St. Paul,

inn.

No Drawing. Filed Nov. 20, 1967, Ser. No. 684,518 Claims priority,application Great Britain, Nov. 22, 1966, 52,310/66 Int. Cl. G03c 1/36,5/26 US. Cl. 96-65 18 Claims ABSTRACT OF THE DISCLOSURE This inventionrelates to coatings of non-light sensitive silver halide materials whichcan be made light sensitive and to the use of these coatings in thereproduction of light images.

The present invention provides a film construction which is essentiallylight insensitive but which can be made light sensitive prior to use.Moreover, this invention also provides a light insensitive filmconstruction which can be repeatedly made light sensitive, imaged andnon-light sensitive. The many uses for such a film construction will beobvious, and some of these uses are described hereinafter.

The novel film construction of this invention is characterized by atleast one layer containing a light insensitive argentohalide complex(i.e. silver-halide complex), said layer upon contact with a proticsolvent. No photosensitive photosensitive silver halide crystals andphotosensitive silver ions, said complex providing light sensitivity insaid layer upon contact with a protc solvent. No photosenstive silverhalide crystals or silver ions can be tolerated in this layer, all ofthe silver being present in the form of the argentohalide complex. Suchargentohalide complexes are shown in Table 1.8 on page 8 of The Theoryof the Photographic Process, 3rd edition, C. E. K. Mees and TH. James(Macmillan Co., N.Y., 1966), and include AgCl Agcl AgBr AgBr AgCl 'BrAgOlBr Aglf, and Agl The films may consist of only the single layeritself, and hence would be considered self-supporting films, or they maycomprise a substrate on which is coated one or more of such layers. Theargentohalide complexes may be most conveniently prepared by reactingsilver halide (i.e. silver chloride, silver bromide, silver iodide or amixture thereof) with excess halide ions provided by a stronglyionizable halide, this reaction being conducted in a dipolar aproticsolvent medium to dissolve all the complex argentohalide and asuificient amount of the strongly ionizable halide to generate enoughhalide ions to complex all of the silver as the desired argentohalidecomplex.

When the layer of the invention is dry, that is to say in the absence ofa protic solvent, it is stable and light insensitive. It can be madelight sensitive by treatment with a protic solvent to give free silverhalide in the coathoe ing. Once the coating has been moistened to makeit light sensitive, it can be exposed to light to give a latent imagewhich can then be developed by an active developer, such asmetol/hydroquinone or phenidone/hydroquinone developer and it is foundthat development takes place very quickly. A particularly convenient wayof moistening the dry coating to make it light sensitive is to moistenit with the developer, since this has the great advantage of increasinglight sensitivity. Also if a highly active developer is used, thedevelopment is virtually complete at the end of the exposure time. Thedeveloped image can then be fixed with a conventional fixer, such as anaqueous solution of sodium thiosulphate.

The advantages of the invented material will be apparent, since the drycoating of the material can be made light sensitive or light insensitiveat will, simply by moistening or drying the coating with a proticsolvent such as water. This change from light sensitive to lightinsensitive is limited by the fact that excess halide ions must bepresent and so one must ensure that the activation and development ofthe coating does not wash these out. With such a coating a number oflight images can be developed one after another on the same coating.

The composition can be conveniently coated onto the photographicsubstrate from solution in a dipolar aprotic solvent and, when it hasbeen dried, the coating is sufliciently light stable to be exposed tosunlight over prolonged periods without detectable change. The coatingcan, however, very easily be made light sensitive by being moistenedwith water, an alcohol or other protic solvent. The moistened coatinghas in fact, a surprising sensitivity to irradiation, particularlyactinic irradiation, e.g. light and X-rays, in the same manner asphotosensiti=ve silver halide.

According to a preferred embodiment of this invention, the argentohalidecomplex is made by dissolving silver bromide or silver iodobromide indimethylsulphoxide or dimethylformamide in the presence of excessbromide ions, which can be supplied by a strongly ionizable halide suchas ammonium bromide, potassium bromide or other alkali metal halide oralkaline earth metal halide. Hydrogen bromide may also be used to supplythe excess bromide ions. This solution is preferably mixed with abinder, such as a synthetic polymer e.g. acrylic acid/ acrylic estercopolymer or gelatin, in order to obtain a tough layer which does notdissolve during aqueous processing. A binder providing a water permeablematrix may be advantageous. In addition, other organic compounds, forexample a normally solid organic compound (e.g. phenylacetdimethylamide,polyvinylpyrrolidone, etc.) or a normally liquid organic compound (e.g.dinonylformamide, etc.) may be included to improve such properties asimage quality. The resulting solution or suspension is coated ontophotographic substrate which may, for example, be glass, paper or atransparent film base. It may also be cast in the form of aself-supporting sheet or film. Both the formulation steps and thecoating operation may be carried out under normal room light, since thesolution of the complex material in the aprotic solvent is not lightsensitive. After drying, the coating or casting is also light stable.

According to another embodiment of the invention the complex is preparedby mixing a silver halide, such as silver bromide, with a stronglyionized halide such as ammonium bromide in water or other protic solventand then crystallizing the complex from the solvent. In the case ofsilver bromide and ammonium bromide the complex compound has thecomposition (NH AgBr the argentohalide complex being AgBr The crystalsof this complex compound are separated from the solvent, and ground,ball milled, homogenized or mixed by ultrasonic vibrations in thepresence of an inert aprotic organic solvent, such as ethyl methylketone, and a polymeric binder such as butyl acrylate/acrylic acidcopolymer to give a suitable composition for coating on the photographicsubstrate. This method of operation has the advantages that the complexcan be obtained in a relatively pure form so that the final coating hasgreater stability to atmospheric conditions such as humidity, and onehas more control over the ultimate graininess of the silver in an imagedeveloped in the coating.

In order to use the coating in the reproduction of a light image, it ismoistened with a protic solvent, for example, water or alcohol, and thisapparently causes precipitation of silver bromide in a form which has ahigh sensitivity to light. Instead of applying the water or alcohol as aliquid to the surface of the coating, the coating can be moistened byexposing it to steam.

In order to improve the sensitivity of the moistened coating toparticular wavelengths of light it may be dye sensitized. This may beeffected by incorporating the sensitizing dye in the coating during thepreparation of the complex material. Alternatively the sensitizing dyemay be in solution in the liquid used for wetting the coating to make itlight sensitive.

If desired chemical sensitizers such as for example gold or sulphursensitizers, antifoggants and other silver halide additives may beincorporated in with the complex material in accordance with theinvention before it is coated onto the substrate.

The invention has wide fields of use in the reproduction of lightimages. In fact, the coating of the invention can apparently be used inany application in which conventional silver halide materials are used.These include, for example, negative and positive black and white cameraprinting materials, microfilms, graphic arts films, color photographymaterials, X-ray films, and office copying materials.

The following examples are illustrations of the preparation and use ofcoatings in accordance with the invention.

EXAMPLE 1 To 88 ml. of dimethylsulphoxide were added 40 g. of ammoniumbromide, 17.6 g. of polyvinylpyrrolidone, 17.6 g. of silver bromide and0.88 g. of silver iodide. The mixture was brought into solution bywarming to 40 C. with efiicient agitation.

Meanwhile, 23.0 g. of gelatin was wetted with 18 ml. of water and setaside until the water was absorbed. ml. of ethanol were added and themixture allowed to stand for 1 hour. The mixture was then melted bywarming and added to the above dimethylsulphoxide solution at 40 C.,stirring until a clear solution was obtained. A further 50 ml. ofethanol was then added, again stirring to obtain a clear solution. Thisfinal addition made the viscosity of the solution suitable for coating.

Chrome alum (8 ml. of 8%) was added to the above solution as a hardenerand the solution was then coated at 1.5 thou. wet thickness onto paperbase and onto polyester film, and dried at 80 to 100 C. As neither thecoating solution nor the coated layers are light sensitive, thisoperation was carried out in room lighting.

The film and paper materials so obtained were insensitive to light overa prolonged period. They became light sensitive when moistened withwater.

A sample of the paper coating was moistened with water during 15 secondsand exposed behind a negative. The exposed material was then developedfor 10 seconds in undiluted Ilford P.Q. Universal developer, rinsed,fixed in sodium thiosulphate solution and washed in running water.Sensitometric tests were carried out, using an exposure of 3390 metercandle seconds to a lamp of color temperature 3040 K. behind acontinuous wedge. These indicated a speed of 0.005 A.S.A.

A second sample of the paper coating was moistened with undiluted IlfordP.Q. Universal developer and exposed behind a negative. Development wasvirtually complete at the end of exposure (2 seconds) and the materialwas then rinsed, fixed and washed as before. Sensitometric tests carriedout as above indicated a speed of 0.1 A.S.A.

A third sample of the paper coating was moistened with undiluted IlfordP.Q. Universal developer, then bathed in an M/l000 aqueous solution of3-carboxymethyl-5-(3- methylthiazolidin-2'-yl p methylethylidene-)rhodanine (ammonium salt) and then exposed and processed as before.Sensitometric tests carried out as described above indicated speed 0.2A.S.A., fog 0.02 and gamma 1.0. Wedge spectrograms were prepared showingthat the increase of speed was due to dye sensitization. The undyedmaterial was sensitive to about 500 III/L while the material dyed asabove was sensitive to about 570 me.

A sample of the film coating was moistened with Ilford P.Q. Universaldeveloper, exposed and processed as described above. This showed aresolving power of 50 lines/mm.

EXAMPLE 2 A solution for coating was prepared as in Example 1, but inplace of dimethylsulphoxide, 176 ml. of dimethylformamide was employed.The solution was then coated at 1.5 thou. wet thickness onto Barytacoated paper base. When moistened with Ilford P.Q. Universal developer(undiluted), sensitometric tests indicated a speed of 0.1 A.S.A.

EXAMPLE 3 A solution for coating was prepared as in Example 1, place ofpolyvinylpyrrolidone, phenylacetdimethylamide (26.4 g.) wasincoroparted. The solution was then coated at 1.5 thou. wet thicknessonto Baryta coated paper base. When moistened with Ilford P. Q.Universal developer (undiluted), sensitometric tests indicated a speedof 0.1 A.S.A.

EXAMPLE 4 Precipitated silver bromide (47 g.) suspended in water ml.)was heated to just below the boiling point of the water. Ammoniumbromide g.) was then added and the mixture stirred until the silverbromide had completely dissolved. On cooling this solution to 50 C., acomplex argentobromide crystallized out as glistening white needles.These were filtered off, separated as completely as possible from themother liquor and dried.

A butyl acrylate/acrylic acid copolymer (3 g., 21.6% acrylic acid) wasdissolved in dry ethyl methyl ketone (60 ml.). Ammonium bromide (1 g.)was added and the mixture was ground in an orbital grinder for 30minutes. Ammonium argentobromide (10 g.) as prepared above was thenadded to the mixture which was then ground for a further two hours. Thesuspension was coated onto a Baryta coated paper at a wet thickness of0.002 inch and dried.

When this coating was soaked in water for 20 seconds, exposed to 2840meter candle seconds of tungsten light through a photographic negative,and developed for 25 seconds in a standard commercialPhenidone-hydroquinone developer (P.Q. Universal developer at a dilutionof 1 part of developer to 4 parts of water) followed by fixation insodium or ammonium thiosulphate solution, it gave a print having animage density of 0.9 upon a stable white background.

EXAMPLE 5 A polyvinyl butyral resin (0.5 g. Butvar B. 76) andpolyvinylpyrrolidone (5.0 g.) were dissolved in dry chloroform (50 ml.).Ammonium bromide (2 g.) was then added and the mixture was stirred forfive minutes. Ammonium argentobromide 10 g.), prepared as described inExample 1 was added and the mixture was ground for three hours in anorbital grinder. This dispersion was then coated onto a Baryta coatedpaper at a wet thickness of 0.002 inch and dried.

This coating was soaked in a Phenidone-hydroquinone developer (P.Q.Universal at a dilution of 1 part of developer to 4 parts of water) for20 seconds and exposed to 7,100 meter candle seconds of tungsten lightthrough a photographic negative. Further development for 25 seconds inthe same developer followed by fixation in sodium or ammoniumthiosulphate solution gave black images of density 0.8 upon a stablewhite background.

When using the films of this invention, if one moistens the layerwithout removing the excess of halide ions provided by the ionizablehalide, the latent image formed upon exposure of the photosensitivesilver halide can be erased simply by drying the layer, e.g. by heating.The layer may then be remoistened with protic solvent, exposed anddeveloped without a trace of the original latent image. This erasabilityfeature permits the use of a protic solvent in the coating compositionfor preparing the film product, since in a reverse reaction halide ionderived from excess ionizable halide converts any silver halide to theargentohalide complex upon drying. For this reason, aqueous gelatinsolution may be included in the coating composition if a gelatin binderis desired in the layer.

Various other embodiments of the present invention will be apparent tothose skilled in the art without departing from the scope thereof.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A light-insensitive film comprising a substrate having at least onelayer thereon containing a light-insensitive argentohalide complexcapable of providing lightsensitive silver halide in said layer uponcontact with a protic solvent, said halide being selected from the groupconsisting of chloride, bromide and iodide.

2. The film of claim 1 in which said layer contains a binder.

3. The film of claim 1 in which said binder is gelatin.

4. The film of claim 1 in which said layer containsphenylacetdimethylamide.

5. The film of claim 1 in which said layer containspolyvinylpyrrolidone.

6. The film of claim 1 in which said layer contains dinonylformamide.

7. The film of claim 1 in which said layer contains a sensitizer.

8. The film of claim 1 in which said light insensitive argentohalidecomplex is ammonium argentobromide.

9. A light-insensitive film having at least one layer containing alight-insensitive argentohalide complex and a halide ionizable in proticsolvent, said complex providing light-sensitive silver halide in saidlayer upon contact with a protic solvent, each said halide beingselected from the group consisting of chloride, bromide and iodide.

10. A light-insensitive film having at least one layer containing alight-insensitive argento halide complex capable of providinglight-sensitive silver halide in said layer upon contact with a proticsolvent, said halide being selected from the group consisting ofchloride, bromide and iodide.

11. A method for preparing the film of claim 10 which comprises reactingsilver chloride, silver bromide, silver iodide, or a mixture thereof ina dipolar aprotic solvent with a strongly ionizable halide to dissolve asufficient amount of said strongly ionizable halide to generate enoughhalide ions to complex all of the silver in the form of the dissolvedargentohalide complex, adding a film-forming binding agent thereto,applying the resulting admixture onto a surface to form a lightinsensitive film, and drying said film.

12. The method of claim 11 in which said film is cast onto said surface,dried and removed therefrom as a selfsupporting film.

13. The method of claim 11 in which said film is coated onto the surfaceof a film base and dried thereon to form a coated film product.

14. A method for preparing the film of claim 1 which comprises reactingsilver chloride, silver bromide, silver iodide or a mixture thereof in aprotic solvent with a strongly ionizable halide to dissolve a sufiicientamount of the strongly ionizable halide to generate enough halide ionsto complex all of the silver in the form of the dissolved argentohalidecomplex, separating said complex from said protic solvent, admixing saidcomplex with a film-forming binding agent, applying the resultingadmixture onto a surface to form a light insensitive film, and dryingsaid film.

15. The process of claim 14 in which said separated complex is admixedwith a film-forming binder agent in an aprotic solvent.

16. A method of image reproduction comprising (a) providing alight-insensitive film having at least one layer containing alight-insensitive argentohalide complex capable of providinglight-insensitive silver halide in said layer upon contact with a proticsolvent,

(b) contacting said layer with said protic solvent to provide saidsilver halide in said layer,

(0) exposing said layer to imagewise radiation to expose said silverhalide, and

(d) developing said exposed layer.

17. The method of claim 16 in which said protic solvent is water oralcohol.

18. The method of claim 16 in which said protic solvent is an aqueousdeveloper.

References Cited UNITED STATES PATENTS 1,503,595 8/1924 Mees 96-652,709,134 5/1955 Jacobs et al. 96-94 3,359,107 12/1967 Goifee et al.96-83 2,752,246 6/1956 Weaver 96-94 3,000,741 9/1961 Pauw et al. 96943,241,970 3/1966 Popeck 96-94 3,436,222 4/1969 Gobran et al. 9694 OTHERREFERENCES Lyalihov Chemical Abstracts, vol. 43, p. 4971 (1949). Bradleyet al., Trans Faraday Society, vol. 63, pp. 426 and 427, 1967.

WILLIAM D. MARTIN, Primary Examiner M. SOFOCLEOUS, Assistant ExaminerUS. Cl. X.R. 96-67, 94

UNITED STATES PATENT OFFICE fiERTIFICATE OF CORRECTEON Patent No. DatedAugust 17, 1971 I t George de W. Anderson and Grahame J. Stehle It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, line 4 delete "layer upon contact with a protic solvent. Nophotosensitive" and insert --layer being free of protic (i.e.non-aprotic) solvent,-;

Column 1, line &7, "protc should be --protic--;

Column line 31, after "Example 1, insert --but in-;

Column 4, line 33, --incorporated--;

Signed and Swim this 5 h day of April 1972.

"incoroparted" should be (SEAL) Attest:

EDWARD M.FLETCHER, JR.

Commissioner of Patents USCOMM-DC 60376-P69 Us. GOVERNMENT Pam-n s mm AM. .l.

